Method and equipment for lubricating a doctor blade in a paper/board machine

Abstract: The invention concerns a method and a device in the operation of a doctor blade in a paper machine / board machine. In the solution, in connection with the doctor blade (11), different quantities of lubricating medium are supplied into different areas of width of the doctor blade, a larger amount of lubricating medium being supplied into the area in which the maximum extent of wear of the doctor blade had been noticed.

Description: The invention concerns a method of lubricating a doctor blade applied against the outer surface of a roll in a paper machine / board machine according to the preamble of claim 1, and a roll provided with a doctor and means for applying a lubricating medium on the outer surface of the roll according to the preamble of claim 5. The doctor blades on the centre roll of the press are worn one-sidely. This comes from a number of reasons, which vary in the cross direction of the machine. Uneven wear is affected, e.g. by the temperature, air flows, etc. factors. Uneven wear rapidly results in replacement of the doctor blade. The wear of the blade is measured, and when the wear exceeds a permitted maximal wear, the blade is replaced. Thus, if the wear of the blade can be made more uniform, it is possible to extend the service life of the blade and to increase the interval of replacement. At present, the lubrication jets of doctors are designed symmetric. However, it has been noticed that, in view of equalization of the wear of blades, a larger amount of lubricant should be introduced in the portion of the blade width that is worn more rapidly. DE 43 03 315 A1 discloses a method and a device for cleaning endless and rotating surfaces in a paper machine. A web of material is brought into contact with the rotating surface and at least one doctor is used the blade of which acts in an area of the rotating surface which is not used by the web of material. In the doctor region wet air is applied to the rotating surface in the area not used by the web of material. Thus, in the present application, it is suggested that the lubrication pipe be divided into sections. It is a second alternative that different quantities of lubricating medium are introduced through separate pipe constructions of different portions of the doctor width. Thus, in the present application, it is suggested that a profiled lubrication jet be used, whereby the wear profile of the blade can be equalized. The method in accordance with the invention of lubricating a doctor is mainly characterized in that different quantities of lubricating medium are applied in different areas of the width of the roll, a larger amount of lubricating medium being applied in the area corresponding to the area of the width of the blade in which the maximum extent of wear of the blade has been noticed. The equipment in accordance with the invention is mainly characterized in that the means for applying lubricating medium comprise means, preferably lubricants ducts, through which different quantities of lubricating medium, preferably water, can be applied to different portions of the width of the roll and thereby supplied to different portions of the width of the blade. The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawing, the invention being, yet, not supposed to be confined to said embodiments alone. Figure 1 is a graphic illustration of the measured wear of a doctor blade in prior-art operation of a doctor, Figure 2A shows a solution of equipment in accordance with the invention viewed in the cross direction of the paper machine, Figure 2B shows an equipment in accordance with the invention viewed in the direction of the arrow K 1 in Fig. 2A, Figure 2C is a sectional view of a jet pipe, Figure 2D is a sectional view taken along the line I-I in Fig. 2B, Figure 3 shows a second, alternative embodiment of a jet pipe in accordance with the invention, Figure 4 illustrates the commonest embodiment of the invention, in which, on the whole, different quantities of lubricant are supplied to different points of the doctor width so as to equalize the blade wear. Fig. 1 illustrates the wear taking place in prior-art doctor operations with uniform and symmetric supply of lubricating medium. The vertical system of coordinates represents the measured blade width. The distance from the tending-side end is indicated in the horizontal system of coordinates as millimetres. It is seen that the measured wear is uneven, increasing towards the driving-side end. Fig. 2A is a side view of a solution of equipment in accordance with the invention. The doctor blade 11 doctors the roll 10 face, and the jet S is introduced from the jet pipe 12 to the forward side of the doctor blade 11. The sense of rotation of the roll is indicated by the arrow L 1 . In the embodiment of the figure, into the jet pipe 12, three lubricant ducts are passed, i.e. the ducts 13a 1 ,13a 2 and 13a 3 , which comprise regulation valves 14a 1 , 14a 2 , 14a 3 for regulation of the flow quantity and, as is shown in the figure, flow meters and pressure gauges C 1 ,C 2 ,C 3 ,D 1 ,D 2 ,D 3 , from which it is possible to monitor the amount of flowing medium passing into each compartment. Through the duct 13a 1 , the lubricating medium is passed into the compartment G 1 in the interior of the jet pipe 12. Through the duct 13a 2 , the lubricating medium is passed into the compartment G 2 in the interior of the jet pipe 12, and through the duct 13a 3 the lubricating medium is passed into the compartment G 3 in the interior of the jet pipe 12. Fig. 2B shows the solution of equipment as viewed in the direction of the arrow K 1 in Fig. 2A. The lubricant jets S 1 are produced from the compartment G 1 , the lubricant jets S 2 are produced from the compartment G 2 , and the lubricant jets S 3 are produced from the compartment G 3 . Thus, in the embodiment of the figure, the jet pipe 12 has been divided into compartment. Through each compartment, the desired quantity of medium flow per metre of doctor width per unit of time is produced. Thus, by regulating the quantity of lubricating medium it is possible to equalize the wear of the doctor blade 11. The amount of lubricant is increased at the portion of the width of the doctor blade at which the most intensive wear has been noticed. Figure 2C is a sectional view of the jet pipe 12. The jet pipe 12 comprises a frame mantle 12a and therein jet nozzles 12b 1 ,12b 2 ... as well as partition walls 12c 1 ,12c 2 and end walls 12d 1 , 12d 2 , by whose means the interior of the jet pipe 12 has been divided into the compartments G 1 ,G 2 and G 3 . The lubricant duct 13a 1 passes into the compartment G 1 . The lubricant duct 13a 2 passes into the compartment G 2 , and the lubricant duct 13a 3 passes into the compartment G 3 . As the lubricating medium, preferably water is used. Moreover, each compartment G 1 ,G 2 and G 3 comprises an emptying plug 20a 1 ,20a 2 ,20a 3 , which is placed underneath when the pipe is installed in its position. When the plug is removed, the compartments G 1 ,G 2 ,G 3 can be emptied of water independently from one another. Fig. 2D is a sectional view taken along the line I-I in Fig. 2B. As is shown in the figure, a water jet is passed from the compartment G 1 through the jet nozzles 12b 1 ,12b 2 ... onto the face 10' of the roll 10 and further, on the roll face, into connection with the doctor blade 11. Fig. 3 shows an embodiment of the invention in which the jet pipe 120, which is shown as a sectional view, additionally comprises an exhaust duct 21a 1 ,21a 2 ,21a 3 passing from each compartment G 1 ,G 2 ,G 3 , in which case each compartment G 1 ,G 2 ,G 3 can also be emptied by running through, by opening the closing valves M 1 ,M 2 ,M 3 connected with said exhaust ducts. Fig. 4 shows an embodiment of the invention in which there are three separate jet pipes, i.e. the jet pipes 120a 1 , 120a 2 , 120a 3 . The amount of lubricating medium supplied by each separate jet pipe is regulated by means of a regulation valve 14a 1 , 14a 2 ,14a 3 of its own.

Claims: Method of lubricating a doctor blade (11) applied against the outer surface (10') of a roll (10) in a paper or board machine wherein a lubricating medium is applied on the outer surface (10') of the roll (10) upstream of the doctor blade (11) with respect to the sense of rotation (L 1 ) of the roll (10) to prevent wear of the doctor blade (11) by supplying lubricating medium to the blade (11), characterized in that different quantities of lubricating medium are applied in different areas of the width of the roll (10), a larger amount of lubricating medium being applied in the area corresponding to the area of the width of the blade (11) in which the maximum extent of wear of the blade (11) has been noticed. Method as claimed in claim 1, characterized in that in the method, a jet pipe (12) is used, which has been divided into compartments and which comprises at least two compartments (G 1 ,G 2 ...), out of which different quantities of lubricating medium are supplied to different areas of the width of the roll (10). Method as claimed in claim 2, characterized in that in the method, the flow quantity per unit of time into/out of each compartment (G 1 ,G 2 ...) of the jet pipe (12) is measured. Method as claimed in any of the preceding claims, characterized in that as the lubricating medium, water is used, which is sprayed onto the face (10') of the roll (10) against which the doctor blade (11) is placed. Roll (10) provided with a doctor having a doctor blade (11) applied against the outer surface (10') of the roll (10) and means (12;120;120a 1 ,120a 2 , 120a 3 ) for applying a lubricating medium on the outer surface (10') of the roll (10) upstream of the blade (11) with respect to the sense of rotation (L 1 ) of the roll (10) so as to prevent wear of the doctor blade (11) by supplying lubricating medium to the blade (11), characterized in that the means (12;120;120a 1 ,120a 2 ,120a 3 ) for applying lubricating medium comprise means, preferably lubricants ducts (13a 1 ,13a 2 ,13a 3 ), through which different quantities of lubricating medium, preferably water, can be applied to different portions of the width of the roll (10) and thereby supplied to different portions of the width of the blade (11). Roll as claimed in the preceding claim, characterized in that the means for applying lubricating medium comprise a jet pipe (12), which has been divided into compartments (G 1 ,G 2 ...), the jet pipe (12) comprising a frame mantle (12a), whereby the desired quantity of lubricating medium can be supplied in connection with the doctor blade (11) from each compartment through jet nozzles (12b 1 , 12b 2 ...) connected with the frame mantle (12a) of the jet pipe (12). Roll as claimed in the preceding claim, characterized in that the jet pipe (12) has been divided into compartments by dividing the space in the interior of the mantle (12a) of the jet pipe (12) into compartments (G 1 ,G 2 ...) by means of partition walls (12c 1 ,12c 2 ...) and end walls (12d 1 ,12d 2 ...). Roll as claimed in claim 7, characterized in that the lubricant ducts (13a 1 ,13a 2 , 13a 3 ) are passed into the interior of the jet pipe (12) through one end of the jet pipe, and that the lubricant ducts passed into the different compartments (G 1 ,G 2 ...) are passed at least through partition walls (12c 1 , 12c 2 ...) / through an end wall (12d 1 ). Roll as claimed in any of the preceding claims 6 to 8, characterized in that each compartment (G 1 ,G 2 ...) comprises an emptying plug (20a 1 ,20a 2 ...) of equivalent, whereby, by opening the plug, it is possible to empty the compartment (G 1 ,G 2 ...) connected with said plug of the lubricating medium in connection with servicing. Roll as claimed in any of the preceding claims 6 to 9, characterized in that , moreover, an exhaust duct (21a 1 ,21a 2 ...) passes from each compartment (G 1 ,G 2 ...) which duct comprises a closing valve (M 1 ,M 2 ...), whereby, when the closing valve (M 1 ,M 2 ...) is opened, each compartment (G 1 ,G 2 ...) can be emptied by means of running through of the lubricating medium. Roll as claimed in any of the preceding claims 8 to 10, characterized in that there is a flow meter (C 1 ,C 2 ...) for the supply of lubricating medium passing into each compartment (G 1 ,G 2 ...) and that the duct passing into each compartment (G 1 ,G 2 ...) additionally comprises a regulation valve (14a 1 ,14a 2 ...) for the flow quantity, whereby it is possible to monitor and to regulate the amount of lubricating medium passed out of the different compartments (G 1 ,G 2 ...).

Inventors: VIERTOLA ARVO, VIERTOLA, ARVO
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1994
Main classification: D21G3
IPC codes: D21G3